Pathology in Practice

Tucker D. Avra Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506.

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Matt Miesner Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506.

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Kelli M. Almes Department of Diagnostic Medicine/Pathobiology and the Kansas State Veterinary Diagnostic Laboratory, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506.

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History

A 2-month-old 22-kg (48.4-lb) Boer doe kid was evaluated because of a 1-week history of proliferative skin lesions that extended from the coronary band to the proximal interphalangeal (pastern) joint on all 4 limbs, an apparently painful gait, and reluctance to rise. Two weeks before the evaluation, the owner noted that the goat appeared to be normal other than having a proliferative lip lesion. The owner soaked the limbs in a solution of magnesium sulfate twice daily for 3 days; after no improvement, the goat was brought in for evaluation. The kid was in a herd of 40 Boer goats. At this time, there were no reports of similar limb lesions in any of its herd mates.

Clinical and Gross Findings

Initial physical examination revealed malodorous and painful plaque-like proliferative areas of alopecia on all 4 limbs; the areas were multinodular, frequently ulcerated or crusted, and multifocally exudative or hemorrhagic. The lesions were located within the interdigital space and circumferentially around the coronary band and extended to the level of the mid-pastern region on all 4 limbs (Figure 1). The lesions were most severe on the thoracic limbs where they extended proximally to the medial aspect of the metacarpophalangeal (fetlock) joints. There were also 4 crusted papules on the left upper lip, each of which measured up to 7 mm in diameter. The goat was reluctant to bear weight on the left thoracic limb. The remainder of the physical examination findings were unremarkable.

Figure 1—
Figure 1—

Photographs of a 2-month-old Boer doe kid that was evaluated because of proliferative skin lesions of 1 week's duration. The goat also had an apparently painful gait and reluctance to rise. A—Gross image of lesions on the caudal aspect of the thoracic limbs. B—Gross image of the lesions on the cranial aspect of the pelvic limbs.

Citation: Journal of the American Veterinary Medical Association 252, 4; 10.2460/javma.252.4.419

The owner declined diagnostic testing at that time, but approved supportive care and empirical treatment for bacterial infection of the distal portions of the limbs. The goat was treated with ceftiofur hydrochloride (2.2 mg/kg [1 mg/lb], SC, q 24 h for 5 days), flunixin meglumine (1 mg/kg [0.45 mg/lb], IV, once), and meloxicam (0.7 mg/kg [0.32 mg/lb], PO, q 24 h for 6 days). The owner was instructed to soak the limbs in dilute povidone iodine solution twice daily for 3 days, keep the goat in a dry area, and return the goat for repeated assessment in 2 weeks.

The goat was returned for a recheck examination 1 month later. The owner had been treating it with a variety of unknown homeopathic sprays and ointments as well as topical and injectable antimicrobial preparations and an anthelmintic. The lesions had become more severe, extended to the level of the fetlock joint on all 4 limbs, and had a more intense odor; also, the lameness was more severe. Multifocal crusty lesions had developed on the axillae, flanks, and trunk. Punch biopsy specimens were obtained from multiple affected locations. The goat was administered tulathromycin (2.5 mg/kg [1.14 mg/lb], SC, once) and discharged to the owner who was instructed to administer meloxicam (0.7 mg/kg [0.32 mg/lb], PO, q 24 h for 6 days) and keep the lesions dry.

Formulate differential diagnoses from the history, clinical findings, and Figure 1—then turn the page→

Histopathologic and Necropsy Findings

Histologic examination of skin samples from the lower lip and distal aspects of the limbs revealed a multifocally markedly hyperplastic epidermis (up to 7 times the normal thickness) with papillary projections and elongated, anastomosing rete pegs that extended into the underlying superficial dermis. The underlying superficial dermis was infiltrated by moderate numbers of lymphocytes and plasma cells with lesser numbers of neutrophils (Figure 2). Multifocally within the stratum spinosum, keratinocytes were markedly swollen with pale eosinophilic cytoplasm exhibiting hydropic change (ballooning degeneration) and nuclear pyknosis. Rarely, keratinocytes contained 1 or more round to oval (maximum dimension, 2 to 10 μm), brightly eosinophilic, intracytoplasmic inclusion bodies (Figure 3). There were multifocal intracorneal pustules within the superficial epidermis and thick surface crusts that contained degenerate neutrophils admixed with cellular debris and coagulated serum. The crusts also contained large numbers of bacterial colonies within abundant fibrin. Biopsy samples were also examined by electron microscopy, which revealed viral particles consistent with poxvirus.

Figure 2—
Figure 2—

Photomicrograph of a section of affected skin obtained from the goat in Figure 1. Notice the extensive surface crusts, epidermal hyperplasia, and a dense lymphoplasmacytic dermal infiltrate. H&E stain; bar = 500 μm.

Citation: Journal of the American Veterinary Medical Association 252, 4; 10.2460/javma.252.4.419

Figure 3—
Figure 3—

Photomicrograph of another section of affected skin from the goat in Figure 1. Notice the proliferative epidermis with ballooning degeneration and intracytoplasmic inclusion bodies (arrow). H&E stain; bar = 50 μm.

Citation: Journal of the American Veterinary Medical Association 252, 4; 10.2460/javma.252.4.419

The histopathologic findings and electron microscopy results for the skin biopsy specimens were consistent with poxvirus infection. Given the diagnostic test results, the goat's unmanageable signs of pain, and the debilitating nature of the lesions, euthanasia by means of an IV overdose of pentobarbital was elected. No additional lesions were detected during postmortem examination.

Morphologic Diagnosis and Case Summary

Morphologic diagnosis: proliferative and ulcerative dermatitis with eosinophilic intracytoplasmic inclusion bodies, serocellular crusts, and intracorneal neutrophilic pustules.

Case summary: atypical parapoxvirus infection (malignant orf) in a Boer goat kid.

Comments

For the goat of the present report, the clinical appearance of the skin lesions, the presence of parapoxvirus in skin samples identified by electron microscopy, and the characteristic histopathologic lesions led to a diagnosis of parapoxvirus infection. The expansive and proliferative nature of the goat's lesions and the failure of the lesions to resolve allowed further characterization of the disease as malignant or atypical orf. Orf has many common names, such as sore mouth, contagious ecthyma, scabby mouth, or contagious pustular dermatitis. A common disease in sheep and goats, orf is maintained in herds via direct and indirect transmission and its ability to survive for long periods of time in the environment and in the scabs of the animal. This client, like many, was familiar with the common form of orf, which occasionally developed within her herd.

The causes of both orf (parapox virus) and goat pox (capripox virus) are part of the family Poxviridae. It is not possible to definitively differentiate parapox virus infection (orf) on the basis of visual identification alone. Goat pox is a foreign animal disease; if introduced into the herd of the present report, it would likely have been associated with a more widespread outbreak and affected goats would have had different clinical features, such as pustular or papular skin and mucosal lesions as well as multiorgan involvement. For the case described in the present report, a diagnosis of parapox virus infection was made, given the clinical signs and gross and histologic lesions.

Orf is an important production disease among sheep and goats because of its economic implications. The oral lesions can cause poor growth as a result of decreased feed intake, and dams with painful lesions of the udder can prevent the offspring from suckling.1 Secondary bacterial infections of affected areas of skin can complicate the disease process and can lead to increased case fatality rates.

In most cases of orf, the lesions are confined to the mouth and spontaneously regress within 2 months. However, in the goat of the present report, the lesions were located on the distal aspects of the limbs, failed to resolve, and continued to proliferate. There are several explanations for the unusual severity of disease in this goat. One possibility was that the goat was immunocompromised. No concurrent disease was diagnosed, although this does not rule out subclinical infections. Infection with Anaplasma phagocytophilum, a cause of tick-borne fever in ruminants, has been shown to predispose lambs experimentally infected with the orf virus to severe contagious ecthyma, compared with effects in control lambs experimentally infected with the orf virus alone.2 There were no signs of A phagocytophilum disease in the goat of the present report; however, a blood sample was not obtained for a CBC, cytologic evaluation, or A phagocytophilum-specific PCR assay. A second possibility was that a variation in the virus resulted in lesions that were more severe than those commonly associated with the orf virus. Although variation in viral strain is a possibility, to date only 1 form of orf virus has been identified.1 Malignant orf in other Boer goat herds has been reported,3 which suggests that the Boer goat breed may also be a predisposing factor.

Atypical forms of orf in both sheep and goats have been described, although they are relatively uncommon in practice.1,3 Therefore, initial patient observation may not lead a clinician to include malignant orf as a differential diagnosis. For the goat of the present report, the owner suspected digital dermatitis. It is unlikely that treatment for digital dermatitis would cure malignant orf, given that many cases of malignant orf described in the veterinary medical literature are unresponsive to treatment.3,4 Other differential diagnoses for the lesions are papillomavirus infection and dermatophilosis, both of which can be ruled out with additional testing.

As a zoonotic agent, the orf virus causes chronic skin lesions in humans, most commonly on the hands.5 The lesions usually self-resolve within 40 days, although the duration is variable. Some patients can develop fever and local lymphadenopathy.1 The zoonotic nature of this disease makes correct diagnosis critical. Such information allows the veterinarian to advise the owner on risks and proper preventative measures. The virus can be transmitted via direct contact with infected tissues or fomites. Therefore, use of gloves during and handwashing after handling of an affected goat as well as sanitation of the halter and other equipment used in the care of the animal are important if a diagnosis of orf is suspected or confirmed.

Cases of malignant orf may first appear as a variation of other common small ruminant skin diseases. Proper diagnosis is important for the identification of orf in a herd, individual patient prognosis, and zoonotic considerations. To attain a diagnosis, it is most practical to submit a lesion crust to a diagnostic laboratory for identification of virus in the tissues via electron microscopy. It is important to note that electron microscopy can diagnose the presence of the virus; however, differentiation between malignant orf and typical orf has to be based on the clinician's evaluation of lesion distribution and persistence.

References

  • 1. Nandi S, De U, Chowdhury S. Review: current status of contagious ecthyma or orf disease in goat and sheep—a global perspective. Small Rumin Res 2011;96:7382.

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  • 2. Gokce HI, Woldehiwet Z. Ehrlichia (Cytoecetes) phagocytophila predisposes to severe contagious ecthyma (orf) in lambs. J Comp Pathol 1999;121:227240.

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  • 3. de la Concha-Bermejillo A, Guo J, Zhang Z, et al. Severe persistent orf in young goats. J Vet Diagn Invest 2003;15:423431.

  • 4. Smith GW, Scherba G, Constable P, et al. Atypical parapoxvirus infection in sheep. J Vet Intern Med 2002;16:287292.

  • 5. Karakas A, Turhan V, Kücükodac Z. Human orf: report of two cases. Turk Silahli Kuvvetleri Koruyucu Hekim Bul 2010;9:551552.

  • Figure 1—

    Photographs of a 2-month-old Boer doe kid that was evaluated because of proliferative skin lesions of 1 week's duration. The goat also had an apparently painful gait and reluctance to rise. A—Gross image of lesions on the caudal aspect of the thoracic limbs. B—Gross image of the lesions on the cranial aspect of the pelvic limbs.

  • Figure 2—

    Photomicrograph of a section of affected skin obtained from the goat in Figure 1. Notice the extensive surface crusts, epidermal hyperplasia, and a dense lymphoplasmacytic dermal infiltrate. H&E stain; bar = 500 μm.

  • Figure 3—

    Photomicrograph of another section of affected skin from the goat in Figure 1. Notice the proliferative epidermis with ballooning degeneration and intracytoplasmic inclusion bodies (arrow). H&E stain; bar = 50 μm.

  • 1. Nandi S, De U, Chowdhury S. Review: current status of contagious ecthyma or orf disease in goat and sheep—a global perspective. Small Rumin Res 2011;96:7382.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 2. Gokce HI, Woldehiwet Z. Ehrlichia (Cytoecetes) phagocytophila predisposes to severe contagious ecthyma (orf) in lambs. J Comp Pathol 1999;121:227240.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 3. de la Concha-Bermejillo A, Guo J, Zhang Z, et al. Severe persistent orf in young goats. J Vet Diagn Invest 2003;15:423431.

  • 4. Smith GW, Scherba G, Constable P, et al. Atypical parapoxvirus infection in sheep. J Vet Intern Med 2002;16:287292.

  • 5. Karakas A, Turhan V, Kücükodac Z. Human orf: report of two cases. Turk Silahli Kuvvetleri Koruyucu Hekim Bul 2010;9:551552.

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